System and method for controlled pumping in a downhole sampling tool

Abstract

A downhole tool designed to be disposed in a borehole of a subterranean formation is provided. The downhole tool includes a probe used to interface with the subterranean formation in order to sample fluid from or to inject fluid into the subterranean formation. The downhole tool also includes a sample flowline fluidly coupled to the probe and used to direct fluid through the downhole tool. The downhole tool further includes at least two volume chambers. These volume chambers each include a first side fluidly coupled to the sample flowline, a second side fluidly coupled to the guard flowline, and a piston separating the first side from the second side. The downhole tool is able to control a flow of fluid from a high pressure environment to a low pressure environment via the at least two volume chambers, the sample flowline, and the guard flowline.

What is claimed is: 
     
       1. A downhole tool configured to be disposed in a borehole of a subterranean formation, the downhole tool comprising:
 a probe configured to interface with the subterranean formation in order to sample fluid from or to inject fluid into the subterranean formation; 
 a sample flowline fluidly coupled to the probe and configured to direct fluid through the downhole tool; 
 a guard flowline configured to direct fluid through the downhole tool; and 
 at least two volume chambers, each volume chamber comprising a first side fluidly coupled to the sample flowline, a second side fluidly coupled to the guard flowline, and a piston separating the first side from the second side, wherein the downhole tool is configured to control a flow of fluid from a high pressure environment to a low pressure environment via the at least two volume chambers, the sample flowline, and the guard flowline. 
 
     
     
       2. The downhole tool of  claim 1 , comprising a reciprocating pump disposed in fluid communication with the guard flowline and configured to pump control fluid through the guard flowline. 
     
     
       3. The downhole tool of  claim 2 , wherein the at least two volume chambers comprise a first volume chamber and a second volume chamber, wherein the reciprocating pump is configured to pump the control fluid from the second side of the first volume chamber to the second side of the second volume chamber to control a flow of injection fluid from the first side of the first volume chamber through the sample flowline and into the subterranean formation via the probe. 
     
     
       4. The downhole tool of  claim 3 , wherein the injection fluid comprises a formation altering chemical, a tracer, or previously sampled formation fluid. 
     
     
       5. The downhole tool of  claim 1 , comprising a first probe configured to draw formation fluid from the subterranean formation into the downhole tool and a second probe configured to inject fluid from the downhole tool into the subterranean formation. 
     
     
       6. The downhole tool of  claim 1 , wherein the downhole tool is configured to perform a micro-frac operation and to control a flowback of micro-frac fluid from the subterranean formation into the downhole tool. 
     
     
       7. The downhole tool of  claim 1 , wherein the at least two volume chambers comprise a first volume chamber and a second volume chamber, wherein the second side of the first volume chamber, the second side of the second volume chamber, and the guard flowline comprise a closed fluid circuit. 
     
     
       8. The downhole tool of  claim 7 , comprising a flow restrictor between the second side of the first volume chamber and the guard flowline, wherein the flow restrictor is configured to restrict a flow of control fluid from the second side of the first volume chamber into the guard flowline to control a flow of fluid from the subterranean formation into the downhole tool.